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Abstract

Hadron beams delivered by normal conducting synchrotrons are highly attractive in various fundamental research experiments as well as in the field of tumour therapy. These applications require fast synchrotron operation modes with pulse-to-pulse energy variation and magnetic field slopes up to 10 T/s. The aims are to optimize the duty-cycle and to minimize treatment times for the patients as well as to provide extremely stable properties of the extracted beams, i.e. position and spill structure. Studies performed at the SIS18 synchrotron at GSI proved that the ring quadrupoles contribute to the deterioration of the slowly extracted beam as well as the dipoles. An attempt has been made to measure the magnetic fields in the synchrotron magnets with high precision and speed comparable to the current measurement with a DCCT used in the power supplies. Adding magnetic field monitoring into the current control feedback loop suppresses the unfavourable dynamic effects from hysteresis and eddy currents. The presentation describes this approach and the results obtained at the HIT [1] synchrotron will be discussed.